Sea Shepherd founder Paul Watson says the anti-whaling activist group tried to stop the carcass from being transferred from the harpooning ship onto another vessel.

He alleges the whalers attempted to ram their boat - the Bob Barker - but backed off.

The Federal Government is arguing in the International Court of Justice that all Japanese whaling is illegal, regardless of where it occurs, and says there is little more it can do.

But Dr Brown says whaling in Australian waters is illegal and the Government should send naval or customs vessels to assert its laws.

"This Government needs to uphold Australian laws. This Government needs to be doing much more to prevent this illegal, violent, bloody, brutal, nasty slaughter of these whales by this Japanese whaling fleet infringing international law," he said.

Dr Brown says the Government should have sought an injunction to stop Japan's whaling while the case in the International Court is ongoing.

"That's going to go on for many months, that legal action has been taking years. It's not effective in stopping the slaughter of those whales down there at the moment," he said.